Adjustable gastric banding apparatus have provided an effective and substantially less invasive alternative to gastric bypass surgery and other conventional surgical weight loss procedures. Despite the positive outcomes of invasive weight loss procedures, such as gastric bypass surgery, it has been recognized that sustained weight loss can be achieved through a laparoscopically-placed gastric band, for example, the LAP-BAND® (Allergan, Inc., Irvine, Calif.) gastric band or the LAP-BAND AP® (Allergan, Inc., Irvine, Calif.) gastric band. Generally, gastric bands are placed about the cardia, or upper portion, of a patient's stomach forming a stoma that restricts the passage of food into a lower portion of the stomach. When the stoma is of an appropriate size that is restricted by a gastric band, food held in the upper portion of the stomach provides a feeling of satiety or fullness that discourages overeating. Unlike gastric bypass procedures, the gastric band apparatus are reversible and require no permanent modification to the gastrointestinal tract.
Over time, a stoma created by a gastric band may need adjustment in order to maintain an appropriate size, which is neither too restrictive nor too passive. Accordingly, prior art gastric band systems provide a subcutaneous fluid access port connected to an expandable or inflatable portion of the gastric band. By adding fluid to or removing fluid from the inflatable portion by means of a hypodermic needle inserted into the access port, the effective size of the gastric band can be adjusted to provide a tighter or looser constriction.
Some non-invasive procedures for adjustment of gastric bands without the use of a hypodermic needle have been proposed. For example, a remotely adjustable gastric band is a medical device which allows a healthcare worker to adjust a gastric band without requiring hypodermic needles to connect to an implanted, subcutaneous access port. A handheld controller can be used to send radio frequency waves for powering and communicating with the implanted device. The implanted device can fill or drain the gastric band as requested by the healthcare worker via the handheld controller.
Such remotely adjustable gastric band systems have some challenges. For example, the implantable pump system has certain design parameters relating to size, power dissipation, flow rate, back pressure, and Magnetic Resonance Imaging (MRI) considerations. These different parameters result in sometimes conflicting constraints for the pump implementation.
Some remotely adjustable pump motors may be powered by a piezo element in a peristaltic pump. In certain circumstances, actuation of the piezo element (or combination of piezo elements) may result in heating of the patient's tissue.
Some other implantable devices have also been disclosed, but these devices suffer from certain disadvantages. For example, Sohn, U.S. Pat. No. 6,417,750, generally discloses magnetically-coupled implantable medical devices, but Sohn does not disclose implantable pumps for use with gastric banding systems.
Hassler, et al., U.S. Pat. No. 7,390,294, discloses a bellows accumulator driven by a piezoelectric system. The system collapses or extends to displace accumulated fluid. The system serves as both a reversible pump and reservoir. However, Hassler utilizes internal electrical power to drive the pump, which may lead to heating of a patient's tissue.
Lorenzen, et al., U.S. Pat. No. 7,396,353, discloses an infusion device and a driving mechanism for delivery of an infusion medium. A coil capable of being electrically activated to provide an electromagnetic field surrounds a piston channel. The piston channel provides a passage for communication of the infusion medium to an outlet chamber located at one end of the piston channel. Because the coil utilizes energy local to the drive mechanism in order to deliver the infusion medium, Lorenzen's device may also lead to heating of a patient's tissue.
Gillies, U.S. Pat. No. 6,834,201, discloses catheter navigation using an MRI device. The internal device utilizes coils that are responsive to an external magnetic field. The current induced in the internal coils generates heat that is then dissipated, so Gillies requires additional components in order to attempt to dissipate the generated heat.
Nelson, et al., U.S. Pat. No. 7,367,340, discloses systems and methods for moving and/or restraining tissue in the upper respiratory system of a patient. But Nelson does not disclose driving an internal magnet with an external magnet. In fact, all of Nelson's magnets are internal. Further, Nelson does not disclose driving a pump to fill or drain an inflatable portion of a gastric band.
Some remotely adjustable gastric banding systems that have been proposed utilize external power and/or transmit telemetric signals through the skin in order to power and/or actuate pumps associated with the remotely adjustable systems. Thus, remotely adjustable gastric banding systems that receive less or no power from an external transmitter are disclosed herein. Further, remotely adjustable gastric banding systems that reduce tissue heating are disclosed herein.